In the related art, there is a seat sliding device for a vehicle that includes a lower rail which is fixed to a vehicle floor and an upper rail which slidably engages with the lower rail and supports a seat upward. In such a seat sliding device, the drive force from a motor or the like as a drive source causes the upper rail to slide with respect to the lower rail.
For example, JP2007-55557A (Reference 1) discloses a seat sliding device that includes a screw rod supported by an upper rail in a rotatable manner and a nut member fixed to a lower rail. The seat sliding device has a configuration in which drive of a motor rotates the screw rod screwed into the nut member.
Further, the seat sliding device of Reference 1 includes a bearing member that holds the screw rod in a rotatable manner at a position between a gear box and the nut member in a longitudinal direction of the upper rail. Specifically, the bearing member is fixed to the upper rail and has a support provided with an insertion hole into which the screw rod is inserted. The support is configured to be pinched between a pair of washers provided on the screw rod and thereby to receive a load in an axial direction thereof.
However, in a case of such a seat sliding device including a bearing member that supports an intermediate portion of the screw rod, there is a possibility that a biased load is generated between the screw rod and the support of the bearing member when the screw rod supported on the bearing member is inclined and rotated. In this manner, there is a concern that operating noise will be generated, or a smooth operation of the screw rod is interrupted.
Thus, a need exists for a vehicle seat sliding device which is not susceptible to the drawback mentioned above.